離子性聚芴衍生物之合成及其在有機發光元件之應用

Abstract

本研究之目的在於合成出含溴烷側鏈之同聚芴高分子P1及共聚芴高分子P2，再進行離子交換反應以得到離子性聚芴材料P1-Br、P1-BF4、P1-PF6、P2-Br、P2-BF4及P2-PF6，探討不同陰離子團基在熱分析、光學及電化學性質之影響，並作為電子傳輸材料以製作多層高分子發光元件。此外亦摻入橘光單體苯并硒二唑合成白光高分子P3，同樣進行離子交換反應，得到離子性聚芴材料P3-Br、P3-BF4、P3-PF6以製備白光電化學元件。 含Br離子性聚芴P1-Br、P2-Br由於產生霍夫曼脫去反應，致使熱穩定性降低，置換成BF4及PF6離子後，可提升高分子之熱穩定性。吸收及放射光譜顯示含有Br之離子性高分子在甲醇會產生藍位移，而含有BF4及PF6離子性高分子在乙腈中會產生藍位移，乃由於高分子在該溶劑之溶解度較高造成高分子鏈之間距離較遠，分子間作用力降低所致；白光高分子P3系列於薄膜態可得到位於430及560 nm之雙放射峰。電化學分析結果顯示含BF4及PF6之離子性高分子其氧化電位明顯下降，因而造成材料HOMO以及LUMO提升。 本研究利用離子性聚芴作為電子傳輸層製作多層高分子發光元件，以MEH-PPV、HMM、HDM、HPM為發光層，證明離子性聚芴的引入，尤其是P1-BF4，確實大幅提升發光元件之亮度及效率。以離子性聚芴製作之藍光及白光LEC元件，亦得到低操作電壓、高亮度及高效率的特點，且不需額外加入鹽類或聚氧乙烯。以上實驗結果說明這些離子性聚芴材料具有高度應用於發光元件之潛力。

The goal of this research is to synthesize homopolyfluorene P1 and copolyfluorene P2 containing bromoalkyl side chains, followed by ionic exchange reaction to obtain ionic polyfluorene materials including P1-Br, P1-BF4, P1-PF6, P2-Br, P2-BF4, and P2-PF6, and to study the influence of different anionic groups on thermal, optical, and electrochemical properties. Those materials were used as electron transporting layer to fabricate multilayer polymer light emitting devices. Besides, orange emitting monomer 2,1,3-benzoselenadiazole was introduced to synthesis white light polymer P3, and ionic exchange reaction was carried out to obtain ionic polyfluorene materials P3-Br, P3-BF4, and P3-PF6 for the fabrication of white light electrochemical cells. The thermal stability of Br-containing ionic polyfluorenes was decreased because of Hofmann elimination. By replacing Br with BF4 and PF6 ions, the thermal stability of polymers was raised. UV-visible absorption and photoluminescence spectra show that Br-containing ionic polymers generate blue shift in methanol, and BF4 and PF6 ionic polymers generate blue shift in acetonitrile. This is because higher solubility of polymer was found in the solvent, resulting in longer distance to decrease molecular interaction between polymer chains. Two emission peaks were found for the white light polymer P3 series located at 430 and 560 nm. Electrochemical analysis shows that oxidation potential of BF4 and PF6-containing ionic polymers was significantly decreased, resulting in increase in HOMO and LUMO of materials. Multilayer polymer light emitting devices were fabricated by using ionic polyfluorenes as electron transporting layer in this research. MEH-PPV, HMM, HDM, and HPM were used as emission layer. Experimental results demonstrated that introduction of ionic polyfluorenes indeed enhanced brightness and efficiency of light emitting devices significantly, especially for P1-BF4. Characters of low operation voltage, high brightness and high efficiency were obtained for blue and white light electrochemical cells by using ionic polyfluorenes, without additional add of salts or poly(ethylene oxide). The above experimental results indicate that these ionic polyflourene materials have highly potential application in light-emitting devices.